Mozzarella cheese is one of the stretched curd cheeses which undergoes a characteristic hot water stretching step to provide both the characteristic oriented fibrous structure and the appropriate melting properties of the finished product. After aging, the normally produced finished product is usefully in cooking, general consumption, and in its most popular use--the production of pizza.
Thus, with an increasing popularity of pizza, the corresponding consumption of mozzarella cheese has also increased. The increase in production has been from 4,819 million pounds in 1983, to 6,634 million pounds in 1992 (United States Department of Agriculture, 1993). This trend towards increasing consumption is only expected to increase in the coming years. Thus, any improvements in the manufacture of pizza that would reduce costs or improve qualitative characteristics would have significant economic value.
Since mozzarella is mainly used for pizza making, its melt characteristics such as blistering, meltability, and stretchability are most important for its consumer acceptance. Mozzarella needs to be aged for 2-4 weeks for break down of proteins through proteolysis in order to develop these desirable melt characteristics. Unaged fresh cheese forms excessive blisters, does not melt on baking, and has limited stretchability. Once aged, the cheese does acquire these characteristics, but the product has to be used since undesirable functional characteristics like excessive free-oil formation and runny texture develop on prolonged storage. Consequently, mozzarella cheese has a very limited shelf life during which its characteristics are suitable for pizza making. The cheese needs to be stored under refrigeration to increase its shelf life to any appreciable period. However, these factors make its transportation and storage very expensive.
Low-moisture (LM), and low-moisture, part-skim (LMPS) mozzarella's exhibit better shred-ability than high moisture mozzarella cheeses and, therefore, are preferentially used as pizza ingredients (Kosikowski, 1978). However, unaged, fresh, LM and LMPS mozzarella's melt poorly to a rubbery, very elastic mass with excessive blistering and limited stretch which is not suitable for pizza. In the first few weeks of refrigerated storage, however, these LM and LMPS cheeses are transformed considerably and attain desirable functionality for pizza making. The shelf-life of this "transformed" mozzarella is normally limited only to a month or less, since the changes which transform its functional characteristics to make these cheeses suitable for pizza making continue, and rapidly during storage to bring about the swift deterioration of shredding and melting properties that are important in pizza making (Kindstedt, 1993).
To solve this problem, others have used combinations of heating, mixing and adding of emulsifiers to achieve various ends, but none of these techniques have produced a mozzarella cheese from fresh curd without aging that can be stored without refrigeration. According to Shimp (1985), the use of emulsifying salts is one of the most effective ways of enhancing cheese functionality. Sodium citrate is known to provide the processed cheese a long elastic structure (Berger et al., 1989). Thermomechanical treatment during cooking and stretching influence functionality of mozzarella cheese (Kindstedt, 1993). In 1957, Kosikowski proposed a process to manufacture processed mozzarella cheese. Ripened mozzarella cheese, the principal raw material, was added with salt, emulsifiers and water, and then cooked in a kettle at 71.degree. C. for 3 min. However, the final cheese demonstrated several poor characteristics, among them was poor stretchability.
U.S. Pat. No. 1,522,383 to Parsons et. al., relates to the low-temperature emulsification of cheese using an apparatus to provide rapid agitation and pressure. The original texture (e.g. and taste) is destroyed and an emulsified texture develops at a temperature of less than 110.degree. F. The objective was to produce an emulsified, unpasteurized cheese, made of a blend of new and aged cheese, which can be melted for cooking purposes without fat separation. In essence a processed cheese product is made from several already made cheeses.
Along the same lines, U.S. Pat. No. 1,523,678 to Wheeler, describes improvements in devices for heat treating cheese and provides means whereby the temperature of the cheese may be rapidly, uniformly and progressively raised.
U.S. Pat. No. 2,021,899 to Schneider, teaches a process and apparatus for the treatment of soft cheeses, containing more than 40% moisture, with the object of improving the flavor, texture and keeping qualities. The method comprises incorporation of emulsifier in cheese, mechanically treating the material at an elevated temperature but not substantially above 200.degree. F., and briefly subjecting the material to heat and then to vacuum without the addition of heat to swell the casein. Again, this patent is for converting already made soft cheeses into a processed cheese.
U.S. Pat. No. 2,733,148 to Russo, describes a method for making regular shaped cheese blocks. This is achieved by cutting the curd in the presence of hot water, heating the cut curd to soft melting stage, mixing the softened curd, paddling the mix after continuous stretching, subjecting the mix to pressure to form a block, and cooling, brining, drying, wrapping and seating the block. This patent is a variant of the current commercial practices of making conventional cheeses, and does not address the problem of additional shelf-life, or non-refrigerated storage.
U.S. Pat. No. 4,066,800 to Rouseneau et. al., teaches a method for producing new cheese foods resembling cheddar or processed cheese at a lower cost. The method used by this patent comprises co-precipitating casein, whey proteins and fat from milk by heating and acid precipitation and modifying the co-precipitate by using additives and extrusion processing to obtain cheddar or a processed cheddar type product. They use an extruder to heat and mix additives such as salt, flavorings and sodium phosphate into the co-precipitate. This process is not suitable for the production of mozzarella cheese.
U.S. Pat. No. 4,669,254 to Muzzarelli, discloses a plant for producing plastic curd mozzarella type cheeses, comprising of a curd chopping device, one kneading device for kneading the chopped curd with an aqueous liquid containing hot water and NaCl, one curd plasticizing device with mechanical implements, feeding the plasticized curd into a tubular sheath, and an apparatus for cutting and closing the sections of tubular sheath filled with plastic curd. Anyone skilled in the art and science of cheese making will recognize that these are the steps and methods used in the conventional mozzarella cheese making process. Generally speaking these steps are necessary to make mozzarella cheese but not invest the cheese produced with any additional shelf-life as a processed mozzarella cheese.
U.S. Pat. No. 5,104,675 to Callahan describes a process for making premium quality Mozzarella/Cheddar cheese having a Mozzarella-like firm texture and Cheddar flavor profile. The process comprises of blending mozzarella (60-75%) Cheddar (25-40%) and sodium citrate (&lt;0.7%), heating to 190-220.degree. F. for 25-45 sec, cooling, and slicing the product. This process, again describes a method for making processed cheese from a blend already made mozzarella and Cheddar cheeses, not from pure mozzarella itself.
French Patent Publication No. 2705534 relates to the manufacture and processing of dairy products with a fibrous texture, like mozzarella cheese. The reference discloses a process of manufacturing cheese which includes mixing water, proteins, carbohydrates, and an agent which slows down the agglomeration process of fibers. The mixture is treated at a temperature between 50.degree. and 100.degree. C. and the mixture is then extruded and cooled.
U.S. Pat. No. 5,234,700 to Barz et. al., relates to a process of making mozzarella cheese in which cheese curd is produced by the standard process and the cheese curd is heated, kneaded, and stretched at 125.degree. to 155.degree. F., such that the cheese has a moisture content in the range of 45 to 60 wt. %. By using this process the cheese can be ready for use immediately after aging.
In another Barz et al., patent, U.S. Pat. No. 5,567,464, relates to a process of making mozzarella cheese which includes manufacturing a cheese curd by standard procedures, heating, kneading and stretching the cheese curd, mixing an emulsifier into the already heated cheese, and forming the heated cheese into a shape. After heating the cheese has a temperature from 110.degree. to 160.degree. F. The shaped cheese is then cooled in cold brine. The improved baking and melting performance seen thereafter are attributed to the addition of an emulsifier (Column 4, lines 19-42).
Despite the efforts of workers in the field, as shown above, mozzarella is still considered a cheese which generally requires a significant period for appropriate aging, and which has limited shelf-life. In addition, this cheese requires to be refrigerated to inhibit the secondary fermentation which causes the deterioration of the cheese quality. Therefore, a need still exists for a mozzarella cheese produced from fresh curd that does not require aging and storage under refrigeration and has a longer shelf life than the currently available mozzarella cheeses.
The goal of the Inventors therefore, was to develop a process for manufacturing processed LMPS mozzarella cheese which requires no aging to attain desirable functional characteristics, does not need refrigerated storage, maintains its functional characteristics during storage, and has prolonged shelf-life. Development of this product promises to lead to many advantages for the cheese manufacturers. First, the product can be used fresh on pizza. Second, elimination of aging and refrigeration will significantly decrease the transportation and storage costs. Finally, the longer shelf-life should facilitate cheese export to overseas for use in pizza restaurants without the need for refrigerated transport and distribution.